Relating to gas separation
A method of purifying gaseous mixtures, for example ternary or quaternary gaseous mixtures, using a sorbent media comprising two or more sorbent materials. The method involves obtaining a target gas from a gaseous composition comprising the target gas, a first gas and a second gas, and optionally further gases by contacting the gaseous composition with the sorbent media to remove at least some of the first gas and at least some of the second gas from the gaseous composition. The sorbent media comprises at least a first sorbent material and a second sorbent material; wherein the first sorbent material has a higher adsorption selectivity for the first gas than for the target gas; and wherein the second sorbent material has a higher adsorption selectivity for the second gas than for target gas. The method may be particularly useful for the separation of pure ethylene, methane or propylene from such gaseous mixtures. A sorbent media and an apparatus for obtaining a target gas from such a gaseous composition are also disclosed.
1 . A method of obtaining a target gas from a gaseous composition comprising the target gas, a first gas and a second gas, the method comprising the step of contacting the gaseous composition with a sorbent media to remove at least some of the first gas and at least some of the second gas from the gaseous composition; wherein the sorbent media comprises a first sorbent material and a second sorbent material; wherein the sorbent media comprises the first and second sorbent materials, and any further sorbent materials, in discrete sections arranged in series; wherein the first sorbent material is an ultramicroporous material comprising a metal organic material, a metal organic framework material, or a porous coordination polymer material and having pores of an average diameter of less than 0.7 nm and has a higher adsorption selectivity for the first gas than for the target gas; wherein the second sorbent material is an ultramicroporous material comprising a metal organic material, a metal organic framework material, or a porous coordination polymer material and having pores of an average diameter of less than 0.7 nm and has a higher adsorption selectivity for the second gas than for target gas; wherein the target gas is a C 1-4 hydrocarbon; and wherein the second gas is ethane.
2 . The method according to claim 1 , wherein the target gas is ethylene, propylene, propane or methane.
3 . The method according to claim 1 , wherein the first gas is acetylene.
4 . The method according to claim 1 wherein the first sorbent material is an ultramicroporous material having a three-dimensional lattice of metal species (M) and linker groups; wherein the metal species (M) are linked together in a first and second dimension by first linker groups (L 1 ) and are linked together in a third dimension by second linker groups (L 2 ) to form the three-dimensional lattice; and wherein one of L 1 and L 2 is an organic linker group and the other of L 1 and L 2 is either an inorganic or an organic linker group; and wherein the ultramicroporous material has the formula M x (L 1 ) 2 (L 2 )Y z wherein x=1 to 3, Y is an inorganic anion and z=0 to 3.
5 . The method according to claim 4 , wherein Mis Cu 2+ , L 1 is 4,4′-bipyridylacetylene and L 2 is TiF 6 2− .
6 . The method according to claim 4 , wherein M is Ni 2+ , L 1 is 4,4′-bipyridine and L 2 is tartaric acid.
7 . The method according to claim 1 , wherein the second sorbent material is an ultramicroporous material of formula Zn 2 (A) 2 (B); wherein A is an amino-substituted heterocyclic ligand and B is a dicarboxylate ligand.
8 . The method according to claim 7 , wherein A is an ion derived from 3-amino-1,2,4-triazole and B is an ion derived from isophthalic acid.
9 . The method according to claim 1 , wherein the second sorbent material is an ultramicroporous material of formula M x (L 1 ) 2 (L 2 )Y z wherein M is Co 2+ or Ni 2+ , wherein x is an integer from 1 to 3, L 1 is an organic linker group, L 2 is a di-carboxylic acid linker or a di-carboxylic acid equivalent linker having an azolate group, Y is an inorganic anion and z is an integer from 0 to 3.
10 . The method according to claim 1 , wherein the gaseous composition comprises a third gas, as an impurity; and wherein the sorbent media comprises a third sorbent material which has a higher adsorption selectivity for the third gas than for the target gas.
11 . The method according to claim 10 wherein the third sorbent material is an ultramicroporous material of formula M(L 1 ) 2 (L 2 ) having pores of an average diameter of less than 0.7 nm; wherein M is Ni, L 1 is pyrazine and L 2 is SiF 6 2− .
12 . The method according to claim 1 , wherein the target gas is obtained with a purity of at least 99 wt %.
13 . The method according to claim 1 , wherein the contacting of the gaseous composition with the sorbent media is carried out at a pressure of from 0.5 to 2 bar and a temperature of from 0° C. to 40° C.